The 28-year-old British man who killed two people in a stabbing spree on London Bridge before police shot him dead had been released from prison after a previous conviction for terrorism offenses, prompting recriminations ahead of an election.Wearing a fake suicide vest and wielding knives, Usman Khan went on the rampage on Friday afternoon at a conference on criminal rehabilitation beside London Bridge. He was wrestled to the ground by bystanders and then shot dead by police. Prime Minister Boris Johnson, who has called a snap election for Dec. 12 and is due to host NATO leaders including U.S. President Donald Trump next week, said it was a terrorist attack and that Britain would never be cowed.Khan, whose family is from Pakistan-controlled Kashmir, was convicted in 2012 for his part in an al-Qaeda-inspired plot to blow up the London Stock Exchange. He was released in December 2018 subject to conditions."This individual was known to authorities, having been convicted in 2012 for terrorism offenses," Britain's top counter-terrorism police officer, Neil Basu, said in a statement. "Clearly, a key line of inquiry now is to establish how he came to carry out this attack."Two people - a man and a woman - were killed in the attack. In addition, a man and two women were injured and remain in hospital, Basu said.Britain's opposition Labour Party, which trails the ruling Conservatives in opinion polls, criticized the government's record on crime on Saturday as police continued their investigation."There are big questions that need to be answered," London Mayor Sadiq Khan, the most senior opposition politician in Britain in a position of power, told Sky News."One of the important tools judges had when it came to dealing with dangerous, convicted criminals... was their ability to give an indeterminate sentence to protect the public," he said. "(That) was taken away from them by this government."ELECTION ATTACKDuring the 2017 election campaign, London Bridge was the scene of an attack when three militants drove a van into pedestrians and then attacked people in the surrounding area, killing eight people and injuring at least 48.Islamic State said its fighters were responsible for that attack, but the British authorities have cast doubt on those claims. The 2017 attack focused attention on cuts to policing since the governing Conservatives took power in 2010.Junior interior minister Brandon Lewis defended an independent decision taken a few weeks ago to lower Britain's terrorism threat level, but said sentencing rules needed to be reviewed."It is right that we do have to look again at the sentencing system around these kinds of violent crimes... We will want to move very swiftly," he said.Friday's attack, just 13 days before an election that could decide the fate of Britain's exit from the European Union, prompted political leaders to scale back campaigning.The campaign so far has focused on Brexit and the health service but is likely to include crime over the coming days as Johnson, who praised the bravery of bystanders who tackled the attacker, seeks to limit the fallout from the incident."This country will never be cowed, or divided, or intimidated by this sort of attack," he told reporters in Downing Street late on Friday.